What skills - experience - which enables the civil engineer to support him becoming a projects manager ?

One should have vision of the total activities involved in the project , its duration , quantum of Men , Material , Equipment resources required and  the priority of execution of them.

They should also have the knowledge of the shortfalls in course of missings .

project management skills in general more practice than knowledge but I would recommend PMP or any project management course, usually in construction leadership is improved in the first few years the next skills you need to focus at is seeing the big picture, planning and budget involvement.